Objective - Assessment of the «duration» of interventions in community services, or rather, of the time between subsequent contacts in community psychiatric services in Lombardy in 1990. The Authors relate the «duration» either to the different professional positions and to some variables, like resources and activities, obtained by the Regional Psychiatric Information System. Design - Descriptive analysis of data stored in the computerized database of the Regional Psychiatric Information System. The «duration» has been calculated on the basis of the ratio between working hours delivered by community services and the number of contacts provided in 1990. After trimming the observations, the «duration» has been related to other variables such as structure, staff and activities. Setting - 52 Regional Psychiatric Unit in Lombardy whose catchment area includes 99 Local Sanitary Districts (USSL) for a total population of 7.600.000 inhabitants. Results - A strong variability of «duration» has come out in differents USSL and for different professional competences. The «duration» is reduced by the increase of patients admitted to the Service, by the number of interventions and by the number of rooms available in the Unit. On the other hand, considering the working hours as a variable, the relation is not linear. Conclusion - Even though this index doesn't concern the quality of interventions, it can represent an useful starting point to evaluate community services. The «duration» seems to be an useful quantitative index to delineate the efficiency of services or rather the capability to provide interventions, saving resources or to deliver as many interventions as possible with such resources.